The present invention relates generally to a wiper control system for an automotive windshield wiper, which automatically controls the operating speed of the wiper in dependence upon rain conditions. More particularly, the invention relates to a wiper control system which can avoid the influence of external conditions on detection of rain conditions.
Published Japanese Utility Model Application No. 57-130747, published on Aug. 14, 1982 discloses an automatic control system for an automotive wiper. The automatic control system includes a vibration pick-up which detects vibrations of the windshield created by the impact of rain drops. The output signal of the vibration pick-up is amplified, filtered and then compared with a threshold to produce a driver signal when the output signal level exceeds the threshold level.
In this wiper control system, since the comparator compares an analog vibration pick-up output with an analog threshold, and since the amplifier, filter and comparator all perform analog processing, they are apt to be influenced by external conditions such as errors in the operational characteristics of the respective circuit elements, or temperature conditions. These influences may cause the wiper operation to deviate from that required.